Conventional fuel systems for internal combustion engines are unable to produce consistant molecular suspensions or emulsions of fuel molecules in the air stream drawn into the carburetor, and large droplets of fuel carried by the air stream into the engine cause inefficient and incomplete fuel combustion within the engine. Therefore, numerous attempts have been made to develop fuel feed systems and carburetor systems which effectively feed liquid fuel at all engine speeds while maintaining a desirable air-fuel ratio. These have resulted in the development of sonic and ultrasonic carburetor systems to achieve intensive atomization of fuel, and these systems have been employed in an attempt to achieve an even dispersion of liquid fuel in the combustion air stream. However, previous sonic or ultrasonic mechanisms have failed to operate effectively within the varying conditions present in the carburization system of an internal combustion engine.
Sonic fuel atomization systems have generally taken two forms. The first such form involves the use of vibrating nozzles through which fuel is directly injected into the airstream of an engine or into some other engine location, such as engine cylinders. U.S. Pat. No. 4,132,203 to D. G. Elpern et al provides a good example of a vibrating nozzle for creating a fuel spray. However, vibrating nozzles have proven ineffective for two reasons. First, if the vibrating nozzle malfunctions, the total fuel system for the engine ceases to operate. Either no fuel is provided to the engine, or a stream of unatomized fuel is fed into the airstream which floods the engine. Secondly, it has been found that the degree of atomization from such vibrating nozzles is somewhat uncontrollable due to a "skating effect" which occurs. When fuel is directed through or across a vibrating unit as opposed to being directed against the unit, a vapor barrier cushion forms and causes unatomized fuel to rapidly move across the active area. This "skating" phenomena exists especially during acceleration transients occurring with an engine using the fuel system.
A second form of sonic fuel atomization system includes a single fuel nozzle which directs fuel against the flat, inclined active surface of a sonic transducer. Although in these systems the fuel is directed so as to impinge to some degree against the active surface of the transducer, the fuel is still not effectively atomized. First, the fuel stream is generally directed at an angle toward the point where the fuel ultimately exits the active surface, so no substantial redirection of the fuel stream is accomplished by the active surface. Secondly, a vapor barrier cushion is formed on the flat active surface, particularly when the fuel is directed against the surface at an angle substantially parallel to the direction of fuel movement across the active surface. In fact, the velocity of the fuel striking the active surface in the direction of fuel flow across the active surface enhances the "skating effect" caused by the vapor barrier, and a large volume of unatomized fuel results.
The problems experienced by the use of conventional sonic fuel atomization systems for normal petroleum fuels are multiplied when these systems are employed as sonic dispersion units for synthetic fuels and other mixtures of solids and liquids. The recent development of synthetic fuels and fuel additives and the desire to use these synthetic fuels in furnaces, conventional internal combustion, diesel and turbine engines, and otherwise as a substitute for petroleum fuel has created a need for a very effective emulsifier. Synthetic fuels often do not burn as well as petroleum fuel, and consequently it is critical that these fuels be thoroughly atomized at a point closely adjacent the point of combustion. In instances where synthetic fuels are mixed with petroleum fuels, it is generally impractical to premix the fuel components in a common supply tank. Not only do some synthetic fuels fail to mix well with petroleum fuels in situ, but it is often desirable to alter the ratio of the mixture in accordance with the operating condition of the fuel receiving unit. For example, if an engine is being fueled, it is important to mix the fuel adjacent the fuel intake of the engine, to variably control the ratio of the mixture, and to effectively emulsify and mix the fuel components before they pass into the engine. It is impossible to effectively accomplish these results with sonic fuel dispersion systems which are not capable of even effectively emulsifying conventional petroleum fuel.